Biological Exuberance: Animal Homosexuality and Natural Diversity

Sexual Virtuosos: Heterosexuality and Homosexuality Compared

The complete pattern of human heterosexuality is not found in any other species (social-class differences in sexual behavior, pair-bonding, face-to-face copulation, hidden menstruallestrous cycles, oral and anal intercourse, etc.), although any single aspect of human heterosexuality can be found in some animal species. The same statement can be made about human homosexuality.

—JAMES D. WEINRICH³⁹

It is ironic that this last assertion about how human beings are unique in their sexual behavior should have been made by the same scientist who commented on how rarely such statements of human uniqueness prove to be true. Indeed, now that more detailed and comprehensive information is available about animal homosexuality, it appears that at least three species rival, if not equal, human beings in the variability and “completeness” of their sexual expression: Bonobos, Orang-utans, and Bottlenose Dolphins. For each of the features mentioned above, an identical or equivalent aspect of behavior can be found, at least in a same-sex context. While none of these species has rigidly stratified “social classes,” there are discernible differences in sexual behavior between animals of different ages and social statuses. Homosexual activity is often more frequent in younger, lower-ranking female Bonobos who have recently joined a new troop, for instance, while younger individuals are often “on the top” during female homosexual interactions and “on the bottom” during male homosexual interactions. There is also some evidence that sexual activity between females occurs more often when they belong to distant rank classes. Adolescent or younger-adult Orang-utans participate in same-sex activities more than older, higher-ranking individuals and also exhibit distinctive heterosexual patterns. Younger male Bottlenose Dolphins tend to form their own groups in which same-sex activity is more common than among pair-bonded individuals—while adult males in this species generally do form lifelong bonds with each other.

Although Bonobos do not have exclusive pair-bonding per se, females do form long-lasting bonds with each other that include sexual interactions; adolescent females also typically pair up with an older “mentor” female when they arrive in a new group and engage in sexual activity most frequently with her. Orang-utans often form pairlike consortships in heterosexual contexts, and similar sorts of associations also occur in homosexual contexts. Sexual interactions between female Bonobos usually occur in a face-to-face position, as do heterosexual (and some homosexual) interactions in Orang-utans, as well as most copulations in Bottlenose Dolphins (for the latter, a “belly-to-belly” position is perhaps a more apt characterization). “Hidden estrous cycles” refers to the fact that no overt physical changes signal the various phases of a woman’s sexual cycle. A female Bonobo’s sexual skin swells with her cycle, although it is present for the majority of the cycle and is not associated specifically with ovulation. Bottlenose Dolphins do not generally give any visual cues as to their sexual cycles or timing of ovulation, nor do female Orang-utans.⁴⁰ In any case, all three species engage in sexual activity throughout the female’s cycle the way human beings do, which is one important consequence of concealed sexual cycles in humans. Finally, Bonobos, Orang-utans, and Bottlenose Dolphins all engage in forms of anal and oral sex (the latter including fellatio in Bonobos and Orangs, cunnilingus in Orang-utans, and beak-genital propulsion in Dolphins).⁴¹